Abstract

Harvest residues are an attractive woody biomass feedstock for bioenergy production. A portion of the total harvest residues are generally left in the cutblock due to technical and profitability constraints. A better understanding of the factors influencing the variability of residue operational recovery rate is important to inform accurately policy development on sustainable forest biomass procurement practices. We compiled the results of field trials from boreal and temperate forests to quantify the range of variation of residue recovery rates and to identify the main
factors explaining this variability. The average recovery rate was 52.2%, with minimum and maximum values of 4.0 and 89.1 %, and a near-normal distribution around the average. The main factor contributing to this variation was country of opera
tions, which encompasses aspects of bioenergy policy and markets, technological learning, and forestry context. A shift in bioenergy policy, a growth in (and a change in access to) bioenergy markets, and upward movements along the technological learning curve could increase residue recovery rates approaching the highest values observed in this study,such as those in Nordic countries (72% residue recovery),
or even higher if economic and technological conditions keep improving. How ever, local stand conditions, especially in North America where natural variability is high among forest stands, may continue to constrain operational recovery of harvest residues. Our results suggest the need for the development of policies that define practices and thresholds based on the ecological suitability of ecosystems, with clear definitions and explicit standards for harvest residue inventory, quantification, and retention.

Plain Language Summary

The objective of this study was to assess biomass harvesting rates (harvested biomass/biomass left on the ground) in clearcutting operations in the boreal and temperate forests in Europe and North America.

The researchers consulted several biomass harvesting studies and determined that the average rate of residue harvesting was 52% for the countries under study. They also noted a large variation in harvesting percentages, ranging from 4% to 90%. This variation is attributable to the forest management methods used in each country. For example, in Scandinavian countries, there are many plantations and the rate of biomass harvesting can be as high as 90%. In North America, because biomass is harvested most of the time in natural stands, the harvesting rate is lower because the amount of biomass that remains on the ground depends to a greater degree on forest conditions prior to the harvest than on the harvesting rate itself.

For this study, logging residues (tree branches and crowns) were the type of biomass harvested.